Lesson 6: Group 17 Elements (Halogens)

This lesson covers Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), and Astatine (At).

• Reactivity: The halogens are highly reactive non-metals, and their reactivity decreases down the group. Fluorine is the most electronegative element.
• Anomalous Behavior of Fluorine: Fluorine’s small size, high electronegativity, and absence of d-orbitals lead to its unique properties, such as the formation of only one oxoacid ($HOF$).
• Important Compounds:
  • Hydrogen Halides: The preparation and acidic strength of $HF,HCl,HBr,HI$. The acidic strength increases down the group.
  • Chlorine: Preparation by the Deacon’s process or electrolysis. Its properties as a bleaching agent and oxidizing agent.
  • Interhalogen Compounds: The formation of compounds between two different halogens, such as ClF3​ and IF7